The present invention relates to a data transmission apparatus and data reception apparatus operating according to a communication protocol specified by ITU Recommendation V.34.
Recently, this type of data communication apparatus has performed data communications using a V.34 modem (28.8 kbps) which is specified by the ITU-T. For example, in a facsimile apparatus, the ITU-T also recommends T30ANEXF (so-called Super G3) as facsimile communication standards using the above V.34 modem for facsimile machines. An image data communication is carried out according to the communication standard (T30ANEXF).
A communication procedure in accordance with the communication standard will be explained based on the sequence chart illustrated in FIG. 1. FIG. 1 is a control signal chart for a procedure for facsimile communication according to the prior art.
In FIG. 1. 13, 9a is a communication procedure for selecting a modulation mode from among a V34 half duplex, V34 full duplex, V17 half duplex, etc. 9b is a communication procedure for implementing line probing to inspect a line and determine various kinds of parameters. 9c is a communication procedure for modem training. 9d is a communication procedure for setting a modem parameter. 9e is a communication procedure for exchanging a facsimile control signal. 9f is a data communication procedure for the primary channel. The upper side in the diagram is a sequence at a calling side, and the lower side is a sequence at a receiving side, and the sequences progress from left to right.
The above communication procedures will be discussed specifically.
First, after a line connection is established, in the communication procedure 9a for selecting a modulation mode, a modulation mode and communication protocol for enabling a communication between a calling side and a receiving side with a V.21 modem (300 bps, full duplex) are selected. A facsimile apparatus using a V.34 modem selects a V.34 communication as the modulation mode and facsimile communication as a communication protocol.
Then, in the communication procedure 9b for line probing, a line inspection is performed by a line probing tone that is transmitted from the calling side and received at the receiving side, and a training parameter is selected based on the result of the line inspection.
In the communication procedure 9c for modem training, the calling side transmits training signals based on the training parameter selected under the line probing communication procedure 9b, while the receiving side receives the training signals, learns a filter coefficient of an adaptive equalizer for correcting the line characteristic and inspects the reception quality of the training signals.
In the communication procedure 9d for selecting a modem parameter, modem parameters are negotiated between the calling side and receiving side in full duplex communication at 1200 bps, and an optimal modem parameter is selected using the modem parameters preset in the apparatus, the result of the line inspection and the inspection of the reception quality of the training signals.
In the communication protocol 9e for a facsimile control signal, facsimile control signals NSF, CSI, DIS, TSI, DCS, CFR, etc. are negotiated in full duplex communication at 1200 bps.
In the data communication procedure 9f, the calling side transmits image data and the receiving side receives the image data, in half duplex communication at 2400 bps to 28.8 kbps. In the case of performing communication at the maximum communication rate of 28.8 kbps, image data can be communicated in approximately three seconds per a sheet of ordinary sized paper.
The aforementioned communication is performed according to the training parameter selected under the communication procedure 9b for communication line probing and the modem parameter selected under the communication procedure 9d for selection of a modem parameter. To correct the line characteristic, a modem at the receiving side executes communication using the filter coefficient that has been learned in the modem training 9b. The series of communication procedure described above enables the optimal data communication according to the line quality.
The above-described prior art structure involves five channels of procedure until starting transmitting image data (hereinafter referred to as pre-procedure) after line is established, and thus requires about 7 seconds. By contrast, since it takes about 3 seconds to transmit a single sheet of image data at the maximum communication rate of 28.8 kbps, the procedure requires over 60% of the entire time of 11 seconds required for transmission of one sheet of an original including a procedure after transmitting the image data of about 1 second. It takes longer to spend for the procedure as the number of transmission/reception lines increases, thereby generating a wasteful time and communication cost.
Accordingly, it is an object of the present invention to provide a data communication apparatus capable of shortening the time for the procedure that spends a relatively long time for setting of various parameters and others by omitting a part of the procedure.
A data transmission apparatus according to the present invention comprises a memory to store control information of a modem for each destination, and a communication control section for executing a short communication procedure by issuing a short communication procedure shift notification signal when the control information is stored at the memory, while executing an ordinary communication procedure by issuing an ordinary communication procedure call signal when the control information is not stored at the memory.
According to the above constitution, when the control information of a modem at a destination address is stored at the memory, it is possible to instantly shift to the short procedure. Therefore it is not necessary to acquire a modem parameter or the like that is necessary for a communication every time during the communication procedure, and it is thereby possible to shorten a communication time.
In addition, in the ordinary procedure, a communication control procedure is performed in accordance with ITU Recommendation V.34, while in the short procedure, a signal pattern that is different from that of a flag sequence specified by Recommendation T.30 is used as the short communication procedure shift notification signal.
According to the above constitution, since a terminal at the receiving side can distinguish a notification signal indicative of shift to the short procedure definitely from other signal specified by ITU Recommendation, it is possible for the terminal to shift to the short procedure assuredly. Specifically, the short communication procedure shift notification signal is a signal of a repeated pattern of xe2x80x9c0011xe2x80x9d.
In addition, the data transmission apparatus of the present invention executes short communication procedure registration processing by the ordinary communication procedure signal, and after the registration, executes the short communication procedure by issuing the short communication procedure shift notification signal.
According to the above constitution, since it is possible to register a modem parameter in the ordinary communication procedure, the modem parameter registration processing is efficiently executed without using a specific procedure in order to enable communications in the short communication procedure to be executed from the next time.
In addition, the data transmission apparatus of the present invention selects the G3 facsimile communication procedure or the V.34 communication procedure corresponding to the transmission data amount so as to communicate.
According to the above constitution, when the transmission data amount is small, it is possible to shorten a communication time by communicating according to the G3 communication procedure instead of the V.34 communication procedure.
In addition, the data reception apparatus of the present invention comprises a reception section for receiving information from the above data transmission apparatus, and notification section for notifying a calling side of control information on a modem acquired at the receiving side in the ordinary communication procedure.
According to the above constitution, the calling side collectively stores the modem parameter that is acquired at the receiving side then notified to the calling side so as not to store the modem parameter at the reception side, thereby enabling an easy management of the modem parameter and an efficient configuration because it is not necessary to store at the receiving side.
The modem parameter acquired at the receiving side represents training time or data concerning an attenuation amount at a predetermined frequency for a modulation data arrangement.
Further, the data are set by a NSF signal in order to enable the receiving side to readily acquire the modem parameter for the short communication procedure. The calling side acquires the modem parameter acquired at the receiving side to make a set with the modem parameter acquired at the calling side and relates the set to a telephone number to store at the memory in which a short dial or the like is stored. Accordingly, it is not necessary for the receiving side to comprise a memory to store the modem parameter, and it is thus possible for the calling side to collectively manage the modem parameter to store.